Axle for rail vehicle having a low-level floor, bogie and corresponding rail vehicle

ABSTRACT

An axle for a rail vehicle including a central shaft, two wheels which are connected in terms of rotation by the shaft and two bearings, each wheel being mounted so as to rotate relative to a bearing about the axis Y of the wheels. The axle further includes at least one cross-piece for reinforcement of the axle in terms of flexion, this cross-piece rigidly connecting the two bearings.

This claims priority to the French application number 06 00834, filed Jan. 30, 2006, and hereby incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to an axle for a rail vehicle of the type comprising a central shaft, two wheels which are connected in terms of rotation by the shaft and two bearings, each wheel being mounted so as to rotate relative to a bearing about the axis of the wheels.

BACKGROUND TO THE INVENTION

Axles of this type are conventionally used for rail vehicles, in particular for urban rail transport of the tramway type. These conventional axles are provided on bogies which support vehicle bodywork whose floor is generally, above the axles, at a height of 520 mm above the upper edge of the rails with standard wheels having a diameter of 590 mm in the new state. In an urban environment, and therefore with no platform, this floor height poses access problems for passengers, for example, in a tramway.

Document EP 1 171 336 describes a rail vehicle having, on the one hand, a lowered floor above the axles, having a height, above the upper edge of the rails, of 450 mm owing to wheels which have a smaller diameter than the standard diameter and, on the other hand, a floor zone of lesser height, at approximately 355 mm above the rails, connected by means of ramps to the floor zone above the axles, this zone of lesser height being a zone which facilitates access for passengers.

There are also crank axles. Axles of this type described, for example, in document EP 911 239, are located below the rotation axis of the wheels, allowing the floor to be lowered in the region of the axles of the wheels owing to a complex arrangement of transmission of engine torques to the wheels. These axles comprise bevel gears and/or step-down gears which allow a rotary connection shaft to be used which is offset parallel with the rotation axis of the wheels.

The disadvantages of these two types of axle are, firstly, the need to use non-standard wheels and, secondly, a high level of complexity and therefore high production cost for the axles.

SUMMARY OF THE INVENTION

An object of the present invention is therefore to provide a vehicle having a lowered floor without the above-mentioned disadvantages.

The present invention provides an axle for a rail vehicle of the above-mentioned type, wherein it further comprises at least one cross-piece for reinforcement of the axle in terms of flexion, this cross-piece rigidly connecting the two bearings.

According to other features of the invention:

-   -   the cross-piece is located at a height lower than the height of         the shaft, relative to the upper edge of the rails;     -   the diameter of the shaft is between 60 and 140 mm;     -   the cross-piece has a cross-section which is at least equal to         that of the shaft;     -   the cross-piece is hollow and the shaft extends inside the         cross-piece;     -   the cross-piece defines, with the bearings, a sealed space         around the shaft.

The present invention also provides a bogie which comprises a bodywork and at least one axle which supports the bogie as defined above.

The present invention also provides a rail vehicle which comprises a body and at least one bogie for supporting the body as defined above.

According to other features of the present invention, in the case, for example, of a tramway:

-   -   the wheels have a diameter of between 530 and 660 mm and the         vehicle comprises a first floor having a height of between 385         and 510 mm above the upper edge of the rails in the region of         the bogie; and     -   the rail vehicle comprises a second floor having a height of         between 335 and 375 mm, the two floors being connected by means         of a ramp with an inclination of between 5 and 10%.

BRIEF DESCRIPTION OF THE FIGURES

The present invention will be better understood from a reading of the following description, given purely by way of example and with reference to the appended drawings, in which:

FIG. 1 is a schematic plan view of a bogie which is provided with two axles according to the invention;

FIG. 2 is a schematic front view substantially in accordance with the arrow II of FIG. 1, illustrating an axle;

FIG. 3 is a profile view of a rail vehicle having two different floor levels; and

FIG. 4 is a view similar to that of FIG. 2, illustrating an axle according to a variant of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The bogie 1 of FIG. 1 substantially comprises a bodywork 5, two pairs of wheels 9, each of which is integrated in an axle 11, and a suspension system 15 which is interposed between the axles 11 and the bodywork 5.

The bodywork 5 is generally H-shaped having two longitudinal members 17 which are parallel with the longitudinal axis X of the bogie 1. Each longitudinal member 17 has two ramped zones 18, the central portion of the longitudinal member between the two axles 11 being lower than the ends of the longitudinal member. The two longitudinal members 17 are connected by means of a transverse central beam 19 which is perpendicular relative to the longitudinal members 17. The bodywork 5 is intended to support a body 20 of a vehicle, for example a tramway vehicle. The body 20 is, for example, articulated to the centre of the beam 19.

Each axle 11 comprises a central shaft 21 which extends transversely along the entire width of the axle. It connects the two wheels 9 in terms of rotation and extends along the axis Y of rotation which is common to both wheels.

Two bearings 22, each located against a wheel 9, support the bodywork 5. Each wheel 9 is mounted so as to rotate relative to a bearing 22.

A cross-piece 23 which can be seen in FIG. 2 and which is, for example, cylindrical with a rectangular cross-section, rigidly connects the two bearings 22 to each other by means of the lower ends thereof, in vertical alignment with the shaft 21. The cross-piece 23 is thus parallel with the rotation axis Y of the wheels 9 and located below the shaft 21. It is slightly spaced from the shaft at a distance i which is advantageously, for a tramway between 80 and 120 mm, for example, in the order of 100 mm.

The two bearings 22 each have a support surface for the suspension system 15.

The wheels 9 have a diameter D which is advantageously between 530 mm and 620 mm, for example, in the order of 590 mm. 590 mm is the standard diameter for tramway wheels in the new state. The diameter of standard wheels 9 may become as low as 530 mm with wear. The wheels 9 are placed on rails 24.

The diameter d of each shaft 21 is advantageously between 60 mm and 140 mm, for example, in the order of 100 mm.

The cross-piece 23 has a cross-section which is at least equal to that of the shaft 21.

Elements for controlling the bogie, such as a speed step-down gear 26 or a motor, for example, are arranged in one or more bearings 22.

The floor 31 of the body 20 of the vehicle, located just above the axle 11, is remote from the axle 11 with a spacing i. The spacing i, which corresponds to the deflection of the suspensions 15, is advantageously between 40 and 80 mm, in the order of 60 mm, for example. The floor 31 has a thickness e which is advantageously between 30 and 70 mm, for example, in the order of 50 mm.

The inner side of the floor 31 is thus at a height h from the peak of the rail which is a function of D, d, e, and i in accordance with the relationship: $h = {\frac{D}{2} + \frac{d}{2} + e + i}$ h is therefore between $h_{\min} = {{\frac{Dmin}{2} + \frac{dmin}{2} + e_{\min} + i_{\min}} = {365\quad{mm}}}$ and $h_{\max} = {{\frac{Dmax}{2} + \frac{dmax}{2} + e_{\max} + i_{\max}} = {530\quad{mm}}}$ for example, in the order of 455 mm.

The beam 19 connects the longitudinal members 17 and extends below the floor 31.

The operating principle of the invention is to optimise the vertical spatial requirement of the axle 11 by reducing it to the maximum extent in terms of height in order to free space in order to lower the floor 31 of the body 20 of the vehicle to the maximum extent.

The traditional functions of the axle 11 are separate in this instance. An axle 11 must generally, on the one hand, connect the wheels 9 and drive them in terms of rotation by transmitting the traction and braking torques to them, the wheels 9 thus rotating together and in parallel and, on the other hand, withstand the flexion forces which are caused by the mass of the vehicle and the bodywork 5 and which are transmitted by the suspension system 15.

The bogie 1 separates the functions of the axle 11 between, on the one hand, the central shaft 21 which performs the first function of the axle and, on the other hand, the cross-piece 23 which performs the second function.

The cross-piece 23 has sufficient inertia to withstand the flexion brought about by the forces originating from the vehicle and the bodywork. The cross-piece 23 does not rotate and only the shaft 21 drives the wheels 9 in terms of rotation.

The only limitation in terms of the sizing of the central shaft 21 is thus the function of driving the wheels 9 by the shaft 21 which can therefore have a smaller diameter than if it were performing the two functions of the axle 11.

Since the height h of the floor 31 of the body 20 above the upper edge of the rails 24 is limited by the radius R/2 of the wheels 9 increased by the radius d/2 of the shaft 21, and by a minimum spacing i, the invention allows the floor 31 to be lowered to the height h of 455 mm, further taking into account the thickness of the floor 31.

Furthermore, an axle 11 allows a simple transmission system, the first function of the axle being retained, owing to the central shaft 21.

As shown in FIG. 3, in the vehicle 33, a ramp 35 having an inclination of less than 10% is advantageously provided in order to connect the floor 31 of the zone above the bogie to a floor zone 39 of lesser height h′. This zone 39 of lesser height h′ is, for example, the access zone for passengers. A relatively low floor level 39 is therefore achieved for the passenger access zone, in the order of 355 mm.

In a variant, each axle comprises two cross-pieces, for example, when (not illustrated) the bearings are located at the outer side of the wheels. Each cross-piece connects the two bearings, the first cross-piece being located in front of the wheels and the second behind the wheels, symmetrically relative to the shaft.

In the embodiment of FIGS. 1 and 2, the cross-piece 23 of each axle 11 is located below the corresponding shaft 21 with being spaced therefrom. The shaft 21 is located outside of the cross-piece 23.

The embodiment illustrated in FIG. 4, in which the reference numerals for elements which are similar to those of FIG. 2 have been retained, differs from that of FIG. 2 in that the cross-piece 23 surrounds the shaft 21. That is to say, the shaft 21 extends inside the cross-piece 23.

The cross-piece 23 is nonetheless located at a height lower than that of the conventional axle for the same application relative to the peaks of the rails 24. More precisely, the cross-piece 23 is produced with a neutral surface of the cross-piece located below the axis of the shaft.

The surface which is neutral in terms of flexion under a vertical load of the cross-piece is intended to refer to the location of the points of zero longitudinal load in terms of flexion under a vertical load brought about by the bodywork 5 and a rail vehicle which is supported on the bodywork.

To this end, the cross-piece 23 has, for example, more material in the lower portion thereof, between the shaft 21 and the peak of the rail, than in the upper portion, above the shaft 21. In the example illustrated, the cross-piece 23 is offset vertically relative to the shaft 21 so that the clearance Jupper between the shaft 21 and the upper inner wall of the cross-piece 23 is less than the clearance Jlower between the shaft 21 and the lower inner wall of the cross-piece 23.

The cross-piece 23 defines, with the bearings 22, a sealed space around the shaft 21 between the bearings 22.

In this manner, the outputs of the bearings 22 at the inner side (at the side of each bearing 22 opposite the adjacent wheel 9), are sealed by the cross-piece 23 and it is not necessary to provide additional sealing means. Only the outputs of the bearings 22 at the outer side must be provided with sealing means. This has the advantage of simplifying the bearings 22 and reducing the production cost of the axle 11.

In this embodiment, the distance i between the shaft 21 and the floor 31 must be sufficient to accommodate the upper wall of the cross-piece 23 (which is, for example, in the order of 10 mm) and provide sufficient clearance Jupper (for example, in the order of 10 mm). The height of the floor 31 is consequently greater than the height which can be obtained with the embodiment of FIG. 2 (for example, greater by approximately 20 mm). 

1-17. (canceled)
 18. An axle for a rail vehicle comprising: a central shaft; two wheels having a wheel axis; connected in terms of rotation by the central shaft; two bearings; each wheel being mounted so as to rotate relative to a respective bearing of the two bending about the wheels axis, the central shaft extending along the wheel axis; and at least one cross-piece for reinforcement of the axle in terms of flexion, the cross-piece rigidly connecting the two bearings.
 19. The axle as recited in claim 18 wherein the cross-piece is located at a height lower than a height of the shaft, relative to an upper edge of rails for the rail vehicle.
 20. The axle as recited in claim 18 wherein the shaft extends inside the cross-piece.
 21. The axle as recited in claim 18 wherein the shaft has a diameter of between 60 and 140 mm.
 22. The axle as recited in claim 19 wherein the shaft has a diameter of between 60 and 140 mm.
 23. The axle as recited in claim 20 wherein the shaft has a diameter of between 60 and 140 mm.
 24. The axle as recited in claim 18 wherein the cross-piece has a cross-section at least equal to that of the shaft.
 25. The axle as recited in claim 19 wherein the cross-piece has a cross-section at least equal to that of the shaft.
 26. The axle as recited in claim 20 wherein the cross-piece has a cross-section at least equal to that of the shaft.
 27. The axle as recited in claim 21 wherein the cross-piece has a cross-section at least equal to that of the shaft.
 28. The axle as recited in claim 22 wherein the cross-piece has a cross-section at least equal to that of the shaft.
 29. The axle as recited in claim 23 wherein the cross-piece has a cross-section at least equal to that of the shaft.
 30. The axle as recited in claim 20 wherein the cross-piece defines, with the bearings, a sealed space around the shaft.
 31. A bogie for a rail vehicle comprising: a bodywork; and at least one axle supporting the bogie as recited in claim
 18. 32. A rail vehicle comprising: a body; and at least one bogie for supporting the body as recited in claim
 31. 33. The rail vehicle as recited in claim 32 wherein the wheels have a diameter of between 530 and 660 mm, and further comprising a first floor having a height of between 385 and 510 mm above an upper edge of rails for the vehicle in the region of the bogie.
 34. The rail vehicle as recited in claim 33 further comprising a second floor having a height of between 335 and 375 mm, the first floor and second floor being connected by a ramp with an inclination of between 5 and 10%. 